Quantum Dot Transfer from the Organic Phase to Acrylic Monomers for the Controlled Integration of Single-Photon Sources by Photopolymerization.

This paper reports on a new strategy for obtaining homogeneous dispersion of grafted quantum dots (QDs) in a photopolymer matrix and their use for the integration of single-photon sources by two-photon polymerization (TPP) with nanoscale precision. The method is based on phase transfer of QDs from organic solvents to an acrylic matrix. The detailed protocol is described, and the corresponding mechanism is investigated and revealed. The phase transfer is done by ligand exchange through the introduction of mono-2-(methacryloyloxy) ethyl succinate (MES) that replaces oleic acid (OA). Infrared (IR) measurements show the replacement of OA on the QD surface by MES after ligand exchange. This allows QDs to move from the hexane phase to the pentaerythritol triacrylate (PETA) phase. The QDs that are homogeneously dispersed in the photopolymer without any clusterization do not show any significant broadening in their photoluminescence spectra even after more than 3 years. The ability of the hybrid photopolymer to create micro- and nanostructures by two-photon polymerization is demonstrated. The homogeneity of emission from 2D and 3D microstructures is confirmed by confocal photoluminescence microscopy. The fabrication and integration of a single-photon source in a spatially controlled manner by TPP is achieved and confirmed by auto-correlation measurements.

One Strategy for Nanoparticle Assembly onto 1D, 2D, and 3D Polymer Micro and Nanostructures.

The integration of nanoparticles (NPs) into photonic devices and plasmonic sensors requires selective patterning of these NPs with fine control of their size, shape, and spatial positioning. In this article, we report on a general strategy to pattern different types of NPs. This strategy involves the functionalization of photopolymers before their patterning by two-photon laser writing to fabricate micro- and nanostructures that selectively attract colloidal NPs with suitable ligands, allowing their precise immobilization and organization even within complex 3D structures. Monolayers of NPs without aggregations are obtained and the surface density of NPs on the polymer surface can be controlled by changing either the time of immersion in the colloidal solution or the type of amine molecule chemically grafted on the polymer surface. Different types of NPs (gold, silver, polystyrene, iron oxide, colloidal quantum dots, and nanodiamonds) of different sizes are introduced showing a potential toward nanophotonic applications. To validate the great potential of our method, we successfully demonstrate the integration of quantum dots within a gold nanocube with high spatial resolution and nanometer precision. The promise of this hybrid nanosource of light (plasmonic/polymer/QDs) as optical nanoswitch is illustrated through photoluminescence measurements under polarized exciting light.